Hydrocarbon conversion system



July 10,-1945. a A JOHNSON 2,379,965

. HYDROCARBON CONVERSION SYSTEM Filed nec. s1, 1940 Gasaz'zze Emana/wma@sEpR/ITOR PIPE sruzs @fari/.2%.

meines July 1o, 194s nrpnocmos coNvsnsIoN srs'rasr Everett A. Johnson,Park Ridge, Ill., assigner to Standard Oil Company, Chicago, Ill., acorporation of Indianl 'Application December si, 194e, serial No.372,509

19 clams. (el. 1st-52)` v Y pended in a regeneration gas and is ilnallyre- This invention relates` to a hydrocarbon conversion system and itpertains more particularly to a system for converting gas oils orheavier hydrocarbons into high quality motor fuels.

Catalytic cracking processes produce high octane number gasoline and lowgravity gas oils. The heaviercomponents of such gas oils may be crackedmore satisfactorily by thermal'processes than by catalytic processes.The gasoline produced by the thermal conversion of these heav ierhydrocarbons is characterized :by a lower octane number than thecatalytically cracked product. Heretofore it has been necessary tosubject the thermally cracked naphtha to a separate conversion step suchas reforming or isoforming in order to increase its clear octane number.An object ofv my invention is to obtain this clear oc- Vtane numberincrease in the thermally cracked naphtha.without the necessityoil-.employing a separate conversion system f A furtherobject of theinvention is to provide an improved methodand means for utilizing acracking catalyst more fully and to greater advantage than it-has beenutilized in any previous conversion system. A further object is toprovide a new and improved integration 'of thermal and catalyticprocesses which will greatly reduce cap-l ital investments andoperating` costs and, at the same time, increase the quality'and yieldsof gasoline obtainable from a given charging stock. A further object isto provide a method and means for simultaneously treatingthermallycrackednaphtha with catalytic conversion prod-4 ucts in a movingcatalyst system so that the cata.

lyst which has already produced some cat,A conversion of the sas oilwill in a later stage sis multaneously eilect cracking of gas oil andoctane improvement of ,the thermally cracked naphtha. A furtherobiect isto' providean improved means ford'controlling the ilnal stage `oicatalytic sas oil cracking ope tion 'and for preventing undesirablereactions erein.

A further object is to provide an improved sys' temi for correlatingsolvent extraction with' therturned for effecting further reaction. Thereaction products are fractionated to separates1 cycle gas oil from thegasolineand lighter hydrocarbons. 'This cycle gas oil may be solventextracted' to remove polycyclic aromatics or other components which maybe V'undesirable in subsequent conversion steps, v i.

The gas oil or gas oil raiiinate is then passed through a.thermalconversion system and the thermal conversion products are roughlyfractionated to remove tar and to separate a naphF tha from one or moregas oil fractions, the latter being charged to either.the\thermalorcatalytic conversion steps either before or after solvent extraction.`The hot'therxnally cracked naphtha either with or without-the additionof-further heat is then introduced into the catalytic con-1` versionstreamat such a point that it will not interfere with the desiredcatalytic cracking of the gas oil and will not itself be over-treated bythe catalyst but will undergo a reforming change which markedly improvesits octane number.

In many cases the hot thermally cracked naph'- .tha may be introducedinto the catalytic cracking reaction stream at the point wherein` theyrstream is introduced into the' separation stage 3^( since the contact ofthe thermally cracked vapors,y in the separator may be suiiicient tomarkedly improve itsoctane number. In other cases the thermally' crackednaphtha may be introduced v inthe ilnal stage orone ofthe latter stagesof the catalytic cracking or in the transfer line leading to'such stageor stages or in the transfer line ieadingirom` the last stage to theseparation stage. In any event, the thermally cracked vapers/willcontact catalyst which has already performed its function in thecatalytic conversion of gas oil and which has become coated witha octanenumber of the thermally cracked naph. Y

mal and catalyticnracking systems whereby dele-` 45 I l system. The useof a separate reforming system terlous materials may be removed bothfrom the `charging and recycle stocks to the thermal and to thecatalytic conversion steps. Other objects et the invention proceeds.

Iri,practicing my invention I` prefer to employ the .so-called iluidcatalyst system -wherein a solid .catalyst is `suspended in reactionvapors duringv the conversion step. is then separated i'romconversion.products. lis next' regenerated carbonaceous deposit and has thus becomepartially spent. IV have found that this spent catalyst is stilleilective to eii'ect an increase in the tha and that thisincrease can beeiected directly in the latterpart of the catalytic-conversion is thuseliminated and the reformed" thermall naphthaisseparated from thecatalyst and Airactionated in the same system with the cracked Myinvention not only provides a means for more complete utilization ofcatalystand for increasing the. clear octane number of thermally crackednaphtha without appreciable additional expense but it provides a meanswhereby unde sirabie reactions may .be inhibited m .the meer stages ofthe catalytic conversion of gas oil. 'I'he invention is applicable tomoving bed catalyst systems as well as to the powdered or fluid typesystems.

The invention will be more fully understood from .the following detaileddescription and from the accompanying drawing which forms a part of thespeciilcation and which is a ilow diagram schematically illustrating apreferred embodiment of my invention.

The charging stock to my system may be a gas oil or heavier hydrocarbonproduced from petroleum or from any other source. Synthetic hydrocarbonsresulting from the Fischer process of carbon monoxide-hydrogen synthesisor hydrocarbons from the ordinary hydrogenation of carbonaceous materialprovide excellent sources for such charging stock. I will describe thefinvention, however, as applied to the conversion of a 35 A. P. I.gravity Mid-Continent gas oil.

The catalyst employed in this system may be an activated clay such-asthe ac id treated .ben-

tonite commercially marketed as Super Filtrol.`

` dried and heated to about 1ooo F. No invention is claimed in anyparticular catalyst and.

since cracking catalysts are well known in the art a further descriptionof them is unnecessary. The best catalysts are of the metal oxide type,particularly of the silica-metal oxide type.

In the fluid type system I prefer to employ the catalysts in the form ofa powder ranging in particle size from about 200 to 400 mesh. Such apowder in compactedform has a density of about .7, i. e., it weighsabout to 45 pounds per cubic foot. When aerated ata gas velocity ofabout .05 to .2 feet per second, the catalyst becomes uent and may havea density of about 20 to 40 pounds per cubic foot. At gas or vaporvelocities of about .3 to 3 feet per second, preferably about 1 to 2feet per second, the catalyst density may be about 10 to 20 pounds percubic foot and I prefer to employ such catalyst density in my reactionand regeneration zones.

Referring to the drawing, the gas oil charge is introduced through line-I0 by pump II to coils asvaaoo fer line. I prefer to employcatalyst-to-oil weight ratios of about 1,:1 to 5:1. for example about3:1. The temperature in the reactor may be 800 to 1000 F., for example925 F.

Reactor I1 may be a cylindrical vessel with a conical inlet and outletrespectively and of such size and cross-sectional area as to retain thenecessary amount of catalyst for effecting the desired amount ofconversion. The cross-sectional area should be such as to insure avertical vapor velocity of about .3 to 3 feet per second if the reactionis to be eifected under the desired dense phase conditions. It should beunderstood, however, that my invention is not limited to any particularreactor size and shape and that it is only necessary to provide acontact of the vapors with a suillcient amount of catalyst to eiect thedesired conversion. For a catalyst holding time in the reactor of about3 minutes the oil contact time may be about 10 seconds in order toobtain about 40% conversion. My invention is not limited to theparticular conditions above recited; generally speaking the vaporvelocities in the reactor should be sui'cient to maintain a catalystdensity therein of `about 1 to 35 pounds per cubic foot, preferabb about10 to 20 polmds per cubic foot. 'I'he amount of catalyst in the reactorfor a given amount of conversion is de' pendent on the activityof thecatalyst which is dependent in turn on its residence time in thereactor. I prefer to use a residence time and amount of catalyst asdefined by the followingr equation:

T=at-s34 where T is -tons of catalyst in the reactor per 100 barrels ofstock charged thereto, pz is a constant ranging from .3 to 3.0,preferably about 1.2, and t is catalyst residence time in minutes in thetotal reactor space.

Vapors carry catalyst from the top reactor I1 through line I8 to reactorI9 at the same rate as catalyst is introduced into reactor I1. ReactorI9 is preferably of larger cross-sectional area so that about the-samevapor velocities may be obtained therein as were obtained in reactor IIin spite of the addition of alarge amount of hot thermally crackednaphtha vapors introduced through line l0. These thermally crackednaphtha vapors may be characterized by octane number of about 65 to 70while the octane number of catalytically cracked naphtha may be about80. The catalyst which has already eifected the catalytic cracking ofgas oil vapors is in accordance with my invention utilized for obtainingan octane number increase on the thermally cracked vnaphtha ofas much as5 to 15 -units and this I2- of pipe still I 3 wherein the oil isvaporized and heated to give a transfer line temperature of about 800 to1100 F., for example, 900 F. anda transfer line pressure of aboutatmospheric to about 50 pounds 'per square inch, preferably about 10 to15 pounds per square inch. e

' As the heated vapor passes throughtransfer line I4, it picks up hotpowdered catalyst from standpipe or catastat I5. .The catalyst isintroduced into the transfer line in amounts regulated. by slide valveor star feeder I6. It should .be

understood, of course, that steam or a mechanical screw or any othersuitable means may be used for introducing the catalyst into transferline I4v and that the catalyst is carried by the vapors in said line toup-iiow reactor |11. 1f desired, the

catalyst may'be injected directly into the ref actor instead of beingintroduced into thetransincrease in octane number is obtained withoutany appreciable loss in thermally cracked naphtha yield. v

s The time of vapor contact in reactor I8 may be only about ,Ik to $60of that required for the catalytic cracklng of gas oil although itshouldbe understood that gas oil cracking takes place in y reactor I9simultaneously with the reforming of the thermally cracked naphtha. Iprefer to introduce the thermally cracked naphtha through line 20 at atemperature of about 900 F. In reactions wherein quenching is desiredthe `temperatures of thisl introduced stream maybe as l'owas 800 or8'15"l F. Usually, however, I-prefer to add heat at` this point in orderto effect a further catalytic cracking of the gas. oil in reactor -ISalong with the reforming of the thermally. cracked naphtha.Forthispurposethetempera asvaeae ture of the added stream may be about950 to 1050 or 1100 F.

Instead of introducing the hot thermally cracked naphtha through line 20I may introduce it through line 2l at an intermediate point of thereactor. In fact, I may use a single reactor in place of reactors I1 andI9 and merely introduce the hot thermally cracked naphtha near the topof said single reactor. This latter expedient is less desirable in densephase operations than in operations wherein there is uniform movement ofthe catalyst through the reactor.

The reaction vapor stream together with suspended catalyst leaves thetop of reactor l through line 22 and is conveyed therein to cycloneseparator 23. The thermally cracked naphtha may be introduced into thisline 22 through line 24 or line 25 or it may be introduced directly tothe separator through line 26. The exact point or points of introductionwill depend partly upon the amount of thermally cracked naphtha vaporsto undergo reforming or isoforming, partly upon the nature of thecatalyst and the extent to which it has previously been coated withcarbonaceous deposit and partly upon reaction conditions. As hereinabovestated, the treatment is only l to lu of that .required for thecatalytic conversion itself.

The catalyst separated from vapors in separator 23 falls into hopper orstripper 21" which in turn discharges the catalyst 'into standpipe orcatastat 28. 'I'his standpipe is aerated by means of an inert gas suchas steam introduced through line 29 and additional gas may be introducedthrough line 30 for maintaining desired aeration or stripping in hopper21. Gases from hopper 21 are vented through line 3l to line 32 which isthe line conveying reaction vapors from separator 23 to further catalystseparators (not shown) lif required and rthence to fractionating tower33.

Gasoline and gases are taken overhead from tower 33 through line 34 andcooler 35 to receiver 55. Gas may be vented from this receiver throughline 31. A portion of the liquids may be recycled through line 3B asreux for tower 33. The rest of the liquid is introduced through line 30to stabilizer 40.

Propane and `lighter gases are taken overhead from thestabilizervthrough line 4I and cooler conversion. I prefer to userelatively high temperatures and low pressures in this conversion stepalthough the pressure and soaking factors should be suillcient to obtainthe desired crack per pass, usuallyabout 15 to 45%, Preferably about 25or 30%. In a Apreferred example, a transfer line temperature of about975 F. and pressure of about 200 to 300 lpounds per square inch may beemployed. Thermal cracking temperature may range from about 850 to 1100F. and pressures may range from aboutatmospheric to 1000 pounds persquare inch.

The thermal cracking may be effected in the coils themselves or in aseparate soaking drum vmethod of operation the heavy gas oil is`recycled to line 49 for further conversion and the lighter gas on ofabout 60o to 'zoo end point is returned through line 60 to line I0.

Gas oil fractions from any or all of lines 48, 58 and 59 may beintroduced through lines 6|, 52 and 63 respectively to solventextraction system 5t. Similarly, the original feed stock to the systemmay be charged to this extraction system through line 65. In theextraction system the gas oil may be countercurrently or in any otherconventional manner extracted with a selective solvent such as sulfurdioxide, nitroparains such as nitro methane and nitroethane,nitroparafn- SO2, benzol-acetone, furfural, SO2-bengel or any othersolvent known to the art for the removal of polycyclic aromatichydrocarbons or any other components which may be detrimental in either`rate stocks or the separate stocks may beseparately or simultaneouslyextracted in a single system. The raffinate or rafiinates from suchsystem or systems maybe introduced through ,line 60 to the thermalconversion system or through line 51 to the catalytic conversion system.Heavy polynuclear extracts are undesirable in the catalytic conversionsystem but may be introduced into the thermal cracking system throughline 68 or Withdrawn through line 69 to storage.

Spent catalyst from catastat 28 is introduced through valve or starfeeder 10 by means of an oxygen containing gas such as' air from line 1linto line 12 and conveyed therein to up-flow regenerator 13. Here againit should be understood that the catalyst may be introduced directlyinto the regenerator. The regenerator may be a cylindrical vesselsimilar in size and shape to reactor i1 since I prefer to burn thecarbonaceous deposit from the catalyst while the catalyst is in thesuspended dense phase condition that is obtainable with the use ofvertical vapor velocities of about 1 or .2 feet per second.

Regeneration temperatures may be held within close limits, preferablybelow 1050 F. by recycling cool regenerated catalyst, by introducingsteam or co'oling gases (provided that this can be done withoutexceeding desired vapor velocities)4 or by the use of heat exchangecoils in the regenerator. Regenerated catalyst is carried out of the topof the regenerator either through line 14 directly to cyclone separator15 or through line 16 and heat exchanger 11. The regeneration gasesseparated from the catalyst in separator 15 are withdrawn through line18 and both heat and catalyst may be recovered therefrom in anyconventional manner.

Catalyst from separator 15 falls to hopper 19 and thence to standpipe orcatastat ll5. Aerating gas is introduced through lines and 8| and suchgas is preferably withdrawn from the top of hopper 19 through line 82.

The hot thermally cracked naphtha vapors from the top of fractionator 51may be passed directly through lines 83 and 84 for introduction into thelast portion of the catalytic reaction system through lines 20, 2|, 24,25 or 26. Alternatively, these hot thermally cracked naphtha vapors maybe passed through line 85 and heat exchangerV 11 before being introducedinto the catalytic system through any of the aforesaid lines. It` shouldbe understood that while heat exchange has been illustrated between thehot naphtha vapors and the hot regeneration gases,

various other modications of the invention will be apparent to thoseskilled in the art from the above description and I do not limit myselfto any of the details hereinabove set forth except as defined by thefollowing claims.

I claim:

1. In a hydrocarbon conversion system wherein gas oil is cracked by acatalyst suspended in gas oil vapors and is subsequently separated fromsaid vapors and wherein a thermally cracked naphtha is produced bythermal cracking of heavier-than-gasoline hydrocarbons Separated fromcatalytically cracked gasoline, the method of increasing the octanenumber of said thermally cracked naphtha which comprises contacting saidthermally cracked naphtha va- .pors at a temperature of about 800 to1l00 F.

with a catalyst that has previously become coated with a carbonaceousdeposit in said gas oil cracking step.

2. The method of converting a heavier-thangasoline Ahydrocarbon chargingstock into large yields of high quality motorfuel which comprisesvaporizing and heating said stock t a temperature of about 800Ato 1100F., suspending a solid catalyst in said heated vapors and contactingsaid vapors with said catalyst -in an elonthermally cracked gas oil toone of said cracking steps,.and commingling thermally cracked naphthavapors and partially spent cracking cat alyst in a later stage of thecatalytic cracking operation, thereby increasing the octane number ofsaid thermally cracked naphtha.

5. The method of converting a hydrocarbon charging stock heavier thangasoline into large yields of high octane number motor fuel, the stepscomprising solvent-extracting the said charging stock, recovering araffinate and an extract therefrom, catalytically cracking saidraiiinate to produce gasoline anda catalytically cracked gas oil,thermally cracking said extract to produce a thermally cracked naphthaand a thermally cracked gas oil, recycling at least a portion of one ofsaid gas oils to one of said cracking steps, and contacting saidthermally cracked naphtha vapors with the partially spent catalyst in alater stage of said catalytic cracking operation whereby the octanenumber of said thermally cracked ,naphtha is increased.

6. In a vcombination thermal and catalytic cracking system the method ofincreasing the octane number of thermally cracked naphtha produced by'thermal cracking of heavier-thangasoline hydrocarbons, which methodcomprises catalytically cracking a charging stock in first and secondzones and introducing hot thermally cracked naphtha vapors at atemperature of about `800 to 1100c F. into said second cata- 40lytic-cracking zone along with partially cracked gated reaction zone,introducing hot thermally crackednaphtha vapors into said reaction zoneat a point in said zone wherein substantial conversion of the chargingstock has already beeny effected whereby catalyst which has alreadyeffected catalytic conversion of charging stock effects reforming ofsaid thermally cracked naphtha vapors, separating the products ofcracking and reforming from said catalyst and vseparating gasoline fromsaid products.

piments of products resulting from the catalytic cracking.

4. The method of converting a hydrocarbon fresh feedheavier-than-gasoline into large 8. 'Ihe method of claim 6 wherein thetime of contact of thethermally cracked naphtha with the crackingcatalyst is within the approximate range of V2 to 1/50 of the time ofcontact of said charging stock with said catalyst.

9. The method of claim-6 wherein the thermally cracked naphtha vaporsare introduced into said second zone at a temperature which is higherthan the temperature of cracked gas oil vapors from the rst zone.

10. The method of claim 6 which includes the i steps of effectingcatalytic cracking by means of a continuously moving catalyst stream,contacting gas oil vapors with said stream in both of said rst andsecond zones andcontacting said thermally lcracked naphtha with saidmoving i stream in only the second of said zones.

EVE'RET'I A. JOHNSON.

